1. Field of the Invention
The present invention relates to a method and apparatus for correcting coordinates so as to arrange a sample in a field of view in a review apparatus for moving a sample stage onto the specified coordinates to review the sample. More particularly, the present invention relates to an apparatus for deciding a position for review based on information of a position of a defect detected by a higher-level checking apparatus like an SEM (Scanning Electron Microscope) based defect review apparatus.
2. Background Art
In semiconductor manufacturing, it is important to find defects appearing during a manufacturing process in early phases and take measures against the defects in order to ensure yield enhancement. In recent years, even slight defects have nonnegligible effects on yields as semiconductors become smaller, hence making the size of defects to be reviewed smaller.
An SEM-based defect review apparatus is an apparatus for reviewing such slight defects. The apparatus generally reviews defects based on positions of the defects detected by an optical checking apparatus. In this way, before the SEM-based defect review apparatus reviews in detail the defects detected by the checking apparatus, the checking apparatus executes the defect detecting processing as preprocessing. So the detecting apparatus is herein defined as a “higher-level” apparatus.
A defect is reviewed manually using the SEM-based defect review apparatus as follows: a sample stage is moved onto coordinates outputted by the higher-level checking apparatus for image pickup at a low magnification (in a wide field of view); after a position of the defect is confirmed visually, the sample stage is moved such that the defect position is in the middle of the field of view; and a defective image is picked up at a high magnification (in a small field of view). These steps have been automated as the ADR (Automatic Defect Review). In the ADR, a defect appearing in a field of view of an image at a low magnification is detected using image processing, and then a sample stage is moved such that the detected defect is in the middle of the field of view to pick up a high magnification image at a relevant magnification for review of details of the defect. From the perspective of the image processing, a low magnification image is preferably magnified to fully magnify the defect for the review. However, a too high magnification may cause the defect to be out of the view field if a deviation of the position is substantial. Because of this, ADR configuration has a difficulty in setting a parameter of a magnification for a low magnification image, so that user experience is needed for the setting. This is not preferable since the ADR steps depend on user's skill based on the user experience.
To address the above problem, JP Patent Publication (Kokai) No. 2001-338601 (2001) proposes a method of efficiently performing a task of setting a magnification for a low magnification image including: a function of visualizing a deviation between a defect position outputted by a higher-level checking apparatus and a defect position detected in the ADR by displaying the deviation as a vector on a wafer map; a function of correcting a coordinate system such that the deviation is minimum; and a function of optimizing the magnification for the low magnification image depending on the amount of the detected deviation. These functions can visualize a deviation, optimize a correction table, and optimize a magnification for a low magnification image.
However, if there are a plurality of higher-level checking apparatuses, or if different deviation tendencies are shown depending on, for example, check conditions or a deviation tendency changes over time even in the case of that there is only a single checking apparatus, the optimal correction result cannot be obtained using a single correction table.